Self-contained hydraulic lash adjuster



March 20, 1962 .l J. VAN sLooTEN 3,025,842

1 SELF-CONTAINED HYDRAULIC LASH ADJUSTER i l f/f ATTORNEY 3 025 842 SELF-CONTAINED HDRULIC LASH ADJUSTER Louis J. Van Slooten, West Olive, Mich., assigner to General Motors Corporation, Detroit, Mich., a corporation of Delaware Filed Feb. 6, 1961, Ser. No. 87,190 S Claims. (Cl. 123-90) This invention relates to hydraulic lash adjusters as are used, for example, in internal combustion engines for taking up play r clearance in the Valve operating train, and particularly to the type which are not fed from an external supply of hydraulic fluid but rather contain their own supply of such fluid and hence are designated selfcontaining.

The lash adjuster of this invention, like conventional practice, comprises telescoping cylinder Iand plunger members between which axial thrust is` transmitted by hydraulic fluid in a pressure chamber, and a reservoir chamber is provided interiorly of the plunger member for receiving leakage fluid from and supplying replenishment fluid to the pressure chamber in maintaining the proper length adjustment of the lash adjuster.

It has long been a problem in devices of this kind to prevent loss of the hydraulic fluid without developing excessive tluid pressures in the reservoir chamber or in tht limited clearance space between the telescoping members, as would cause malfunctioning through interference with adjustments of the volume of fluid in the pressure chamber to maintain the proper overall length in the valve or other operating train of the engine.

Various types of positive seals have heretofore been proposed for preventing such loss of the initial quantity of the fluid through escape between the telescoping surfaces of the cylinder and plunger members, which seals have generally proved either ineffective for suiliciently long `duration or have proved too costly for use in high volume production. Also, in certain of such positively sealed arrangements it has been necessary to include a quantity of air in the reservoir chamber as a cushion against excessive build up of pressures therein and this air has the disadvantage 0f tending to emulsify the hydraulic fluid `and enter the pressure chamber with consequent Iloss of thrust in the operation of the engine valve by the lash adjuster.

It is the principal object of my invention to eliminate such disadvantages by the inclusion of means within the reservoir chamber to reversibly soak up that portion of the volume of hydraulic fluid therein which varies during relative reciprocation of the plunger and cylinder members in operation. I have found that by employing a body of reticulated material, as for example wire mesh, it is possible to eliminate the need for sealing of the plunger and cylinder members beyond what is afforded by their relatively close sliding fit, while obtaining all the desirable features of a self-contained lash adjuster wherein both excessive pressure build up and aeration of the hydraulic fluid is prevented. In its more specific form, the lash adjuster also may include an air vent at the upper end of the reservoir chamber and a filter of porous material between this vent and the reticulated material to facilitate elimination of lair which may be drawn into the reservoir chamber during operation and to more positively insure against loss of hydraulic fluid through the vent.

A better understanding of the means for carrying out the invention will be had from the following description of a preferred embodiment, selected for illustrative purposes, having reference to the drawing wherein:

FIGURE l is a transverse view partly in section and partly in elevation through the valve operating gear of ited States Pate an internal combustion engine showing the lash adjuster installed between the valve operating cam and push rod.

FIGURE 2 is an enlarged cross-sectional view of the lash adjuster shown in FIGURE 1, with portions of its associated push rod and driving cam indicated in broken outline.

The lash adjuster designated generally by the numeral 1 is shown arranged for reciprocation by the usual camshaft 2 in the engine crankcase 3. Lift movements are transmitted by a pus-h rod 4 to a valve rocker 5 mounted on the engine cylinder head 6, the rocker effecting an opening of an engine poppet valve 7 against a return spring 8.

As shown in FIGURE 2, the lash adjuster comprises inner and outer generally cup-shaped cylinder and plunger members, 9 and lll, respectively, in nestably slidable relation. Between their closed ends is a pressure chamber 11 in which hydraulic fluid acts to transmit thrust during each lift stroke of the cam 2. The plunger member 10 is hollow, forming a reservoir chamber 1.2 interiorly thereof which is connected with the pressure chamber 11 by passage means, including flow restricting means, now to be described.

A passage 13 extends through the closed end of the plunger and a check valve in the form of a ball 14 is loosely retained opposite the end of the passage by a cage 15 so that fluid may flow into the pressure chamber from the reservoir chamber 12, but not in the reverse direction. The numeral 16 indicates a spring which biases the plunger member outwardly of the cylinder member and serves also to position the cage 15 on the plunger member. The plunger member has its side walls pierced by one or more ports 17 opposite an annular groove 18 encircling the plunger member. A slight clearance exists between the slidably fitted external side surfaces of the plunger member and the internal side surfaces of the cylinder member, through which clearance some leakage of hydraulic fluid (eg. lubricating oil) from the pressure chamber 11 will occur during each lift stroke of the cam 2 when the check valve 14 is closed against flow through the passage 13. This leakage or leakdown fluid is collected in the groove 1S and enters the plunger member through the port or ports 17. On each return stroke of the cam, and during its subsequent dwell period, such fluid as has leaked from the pressure chamber during the previous lift strokes is replenished by fluid llowing past the open check valve 14 through the passage 13 into the pressure chamber 11.

Thrust is transmitted to and from the push rod 4 by a push rod seat member 19 shown as having a flange 20 resting on the upper open end of the plunger member 10. Within the upper portion of the reservoir chamber 12, extending above the height of the upper side of groove 18, is a body of reticulated material 21 having its interstices in open communication for ingress and egress of hydraulic fluid. It will be noted this body 21 is spaced from the passage 13 in the bottom of the plunger member so that an ample amount of fluid is readily available for replenishment of the pressure chamber 11 via the passage 13 and check valve 14 as the plunger member moves upwardly in the cylinder member to take up clearance between the cam 2 and the engine poppet valve 7 when the latter reaches its closed position shown (FIG- URE 1). The relative position of the plunger member longitudinally of the cylinder member shown in FIGURE 2 is its normal or mean operating position. An upper limit stop, shown in the form of a snap ring 22 engaging an internal groove 23 in the cylinder member above the push rod seat member 19, is provided for retaining the lash adjuster in assembly when removed from the engine. The closed end of the cylinder member, shown in the form of a foot piece 24, welded or otherwise sealingly xed to the side walls of the cylinder member and having an annular reduced diameter portion 25 extending upwardly around the plunger return spring 16, serves as a lower Ilimit stop for the plunger member 10. During an engine. shutdown, in event the lash adjuster cornes to rest on the nose 2 of the cam the force of the engine valve spring 8 acts to cause the plunger member to gradually leakdown against this foot piece stop 25.

A predetermined quantity of hydraulic iiuid is contained in the lash adjuster such that its volume is sufficient to completely ll the pressure chamber 11, passage 13, port 17, groove 18 and that portion or the reservoir chamber l2 below the reticular body 2li-when the plunger member is` in its uppermost or outermost position against the snap ring Z2. This quantity of hydraulic fluid may be such that its upper level in the fully raised position of the plunger member extends above the lower extremities of the body 21, but since it is important that the interstices of the reticuilated body have an aggregate volume to accommodate the increased volume of hydraulic iluid entering the reservoir chamber as the result of displacement of uid from the pressure chamber 11 during movement of the plunger member to its innermost or lowermost position against the stop 25, the height of iluid in the extended condition of the lash adjuster should not exceed that which will enable the body 21 to receive the luid displaced by the plunger member in moving to its innermost position.

A certain amount of air exists in the interstices of the upper portion of the body 21 at all times except when the plunger member is in its innermost position as described during an engine shutdown, however such air is prevented from emulsifying the hydraulic fluid by the action of the body 21 in damping or baffling agitation of the iluid. The approximate plane of demarcation between the hydraulic fluid and the air when the plunger member is in its mean. operating position is indicated by the line 26 in FIGURE 2. It will be noted that, in the normal operating position of the plunger member shown in FIGURE 2, this plane of demarcation is located approximately equi-distant between the upper and lower extremities of the reticular body 2.1, to which plane the fluid rises in the reservoir chamber from the height of the upper side of groove 18 in response to inward or downward movement of the plunger member from its outermost position against the snap ring 22. Should the plunger member fully leak down to the foot piece stop 25 during an engine shutdown, the iluid level or plane of decarcation (line 26) will rise to a height preferably not exceeding the height of the upper extremities of the reticular body 21.

To maintain a pressure in the reservoir chamber 12 approximately atmospheric there is provided a vent opening Z7, shown as a central hole extending through the seat member 19 and connecting with one or more slots 28 in the seating surface of the latter for the push rod 4. Also, to additionally insure against loss of hydraulic fluid through the vent, a llter 29 of porous material is placed between the thrust member 1eand the body 21 so as to extend across the vent hole 27. This filter may be made of sintered aluminum powder or the like, of such grain size as to have a porosity which will accommodate passage of air therethrough but be substantially impervious to passage of the hydraulic luid used.

Since the lash adjuster as described is adapted to maintain substantially atmospheric pressure at all times within the reservoir chamber there is no need to seal against iluid leakage between the upper ends of the cylinder and plunger members (beyond such sealing effect as exists by 4reason of the close-sliding tit therebetween). The reticulated material of body 21 operates to prevent agitation of the hydraulic fluid in the reservoir chamber as would otherwise result in aeration of the fluid, yet enables the upper end of the reservoir chamber to be vented to atmosphere to prevent excessive build up of pressure.

While the invention has been disclosed in but a single physical embodiment for purposes of illustration, it is appreciated that various minor changes and rearrangements of the parts may be made without departing from the spirit and scope of the invention as defined in the following claims.

I claim:

1. In a hydraulic lash adjuster, relatively movable cylinder and plunger members dening a pressure chamber opposite one end of the plunger member and a reservoir chamber interiorly of the plunger member, passage means for the llow of iluid in each direction between said chambers including means restricting flow `from the pressure chamber to the reservoir chamber relative to flow in the opposite direction, a body of reticulated material Within the reservoir chamber and spaced from said ilow restricting means, said passage means and the portion of said reservoir chamber externally of the outer extremities of said body and said pressure chamber when the plunger member is in its operative position most outwardly of the cylinder member having an aggregate predetermined volume, and a quantity of substantially incompressible fluid of substantially said volume disposed within said chambers and passage means, said body having interstices in iluiid communication with said reservoir chamber portion Iand of aggregate volume to receive substantially the volume of fluid displaceable `from the pressure chamber by the plunger member in moving from its outermost to its innermost operative position in the cylinder member.

2. In a hydraulic lash adjuster, relatively movable cylinder and plunger members defining a pressure chamber opposite one end of the plunger member and a reservoir chamber interiorly of the plunger member, passage means for the flow of fluid in each direction between said chambers including means restricting llow from the pressure chamber to the reservoir chamber relative to flow in the opposite direction, and a body of reticulated material within the reservoir and spaced from said ilow restricting means, said body having interstices in lluid communication with the reservoir chamber and of aggregate volume to receive substantially the volume of lluid displaceable from the pressure chamber by the plunger member in moving from its outer-most to its innermost operative position in the cylinder member.

3. In a hydraulic lash adjuster, generally cup-shaped cylinder and plunger members in telescopic nested relation deining a pressure chamber between their respective closed ends and a reservoir chamber interiorly of the plunger member, lirst passage means accommodating a relatively slow rate of fluid flow from the pressure chamber to the reservoir chamber during movement of the plunger member inwardly of the cylinder member, oneway passage means accommodating a relatively rapid rate of fluid flow from the reservoir chamber to the pressure chamber during movement of the plunger member outwardly Iof the cylinder member, a quantity of hydraulic lluid iilling both said passage means and said chambers to a predetermined level in the reservoir chamber when said plunger mem-ber is in its outermost operative position in the cylinder member, a body of recticular material in the reservoir chamber having interstices accommodating reception of fluid rising above said Alevel as the result of displacement of fluid from the pressure chamber by the plunger member moving toward its innermost operative position in the cylinder.

4. In a self-contained hydraulic lash adjuster, a cylinder member closed at one end, a hollow plunger member slidably reciprocable in the cylinder member, a quantity of hydraulic fluid in said cylinder and plunger members, said plunger member having its end adjacent said closed end of the cylinder member provided with a passage for llow of said fluid, a check valve for said passage openable toward said closed end, said plunger member having side clearance in the cylinder member and a port connecting said clearance with the interior of the plunger member at a distance outwardly of the cylinder member from said plunger member passage for ow of said iluid, one of said clearance and port having capacity for a predetermined rate of ow of said uid, the opposite end of said plunger member having an opening, a tilter of porous material within the plunger above said port and extending across said opening, said lter materia-l having a porosity accommodating ilow of air therethrough but substantially impervious to flow of said uid, an a body of recticular material within the plunger member adjacent said filter and spaced from said passage, said quantity of said fluid being selected to fill said cylinder and plunger members including said port and passage to substantially the height of the lower extremities of said body when the plunger member is in its operative position most outwardly of the cylinder member, Said body having interstices in open communication for ingress and egress of said fluid and substantially of aggregate volume to accommodate the volume of Huid displaceable from the cylinder member by the plunger member in moving to its innermost operative position therein.

5. In a self-contained hydraulic lash adjuster having generally cup-shaped cylinder and plunger members in slidably nestabfle relation deining a pressure chamber between their bottom ends and a reservoir chamber interiorly of the plunger member, said plunger member having a check valve controlled passage in its bottom end for oneway ow of hydraulic uid from the reservoir chamber to the pressure chamber during outward movement of the plunger member in the cylinder member and a side port for returning to the reservoir chamber fluid escaping between the sides of the members from the pressure chamber during inward movement of the plunger member in the cylinder member, and an external thrust transmitting member engaging the plunger member at its open end, the improvement wherein said thrust transmitting member denes a passage venting said reservoir chamber, and said plunger member is provided with a body of reticular material within said reservoir chamber and spaced from said check Valve controlled passage, said body having interstices in open communication with said reservoir chamber for ingress and egress of hydraulic uid and of aggregate volume to accommodate reception of hydraulic tluid displaceable by the plunger member in moving from its outermost to its innermost operative position in the cylinder member, said lash adjuster containing a quantity of hydraulic iluid to substantially fill said pressure chamber, said port, said check valve controlled passage and the portion of said reservoir chamber between said check valve controlledpassage when said plunger member is in its outermost operative position in the cylinder member.

6. The hydraulic lash adjuster of claim 5, having a filter between said body and venting passage of porous material having a porosity accommodating flow of air and substantially impervious to flow of said hydraulic uid therethrough.

7. In a hydraulic lash adjuster, relatively movable members dening a pressure chamber for lluid in thrust transmitting relation between the members and a reservoir chamber for fluid ilowing to and from the pressure cham/- ber, passage means for the flow of lluid in each direction between said chambers including means restricting flow from the pressure chamber to the reservoir chamber relative to ow in the opposite direction and a body of material within said reservoir chamber having interstices in open communication for ingress and egress of fluid in the reservoir chamber, the aggregate volume of said interstices being at least sufcient to accommodate the volume of fluid displaceable from the pressure chamber by relative movement of the members, and a quantity of hydraulic iiuid of volume at least as great as the aggregate volurne of said chambers and passage means exclusive of said interstices.

8. The invention of claim 7, wherein said reservoir chamber has a Vent open to the exterior of the lash adjuster, and a lter pervious to air but impervious to said hydraulic uid is disposed between said vent and said body of material.

References Cited in the le of this patent UNITED STATES PATENTS 2,140,826 Bettison Dec. 20, 1938 

